A Simple Method to Check the Reliability of Annual Sunspot Number in the Historical Period 1610-1847

TL;DR

This paper introduces a straightforward method to verify the reliability of historical annual sunspot numbers by examining their relationship with active days, identifying inconsistencies in the data series from 1610 to 1847.

Contribution

It presents a simple, effective approach to detect data inconsistencies in historical sunspot records, highlighting specific problematic periods in the 17th and 18th centuries.

Findings

Detected inconsistencies before the Maunder minimum.

Identified anomalies in the year 1652 during the Maunder minimum.

Uncovered issues in the 1790s related to the 'lost' solar cycle.

Abstract

A simple method to detect inconsistencies in low annual sunspot numbers based on the relationship between these values and the annual number of active days is described. The analysis allowed for the detection of problems in the annual sunspot number series clustered in a few specific periods and unambiguous, namely: i) before Maunder minimum, ii) the year 1652 during the Maunder minimum, iii) the year 1741 in Solar Cycle -1, and iv) the so-called "lost" solar cycle in 1790s and subsequent onset of the Dalton Minimum.